There always seems to be IC's for sale. Why is this part so readily swapped around? I get turbos or even exhaust as they change so many parameters, but unless substantially moving up air flow or changing the particular use of the car (one mile vs road race)I don't get it.

Every IC design swears to improve everything, even cheap off shore Ebay ones and obviously some designs fall short. But there are typically several good name/nice sized IC's for sale. After all the trouble to install/mod and tune I'm just surprised so many make it back to market.

Any insite? Are guys simply buying easy to install ones and then searching for ones with more volume or efficiency ?